Critics call that an “efficiency gap,” which can only be explained by partisan gerrymandering. Now before the high court, they hope to find a way to close the gap.

Conservative groups argue that there is no way to estimate what each party “should” win in a fair election. The redistricting tests that have been proposed to close the “efficiency gap” in Wisconsin, they say, are arbitrary.

“Leftists want the courts to overturn district lines if not enough Democrats win,” said Tom Fitton, president of Judicial Watch, a conservative watchdog group that has filed briefs defending Wisconsin’s electoral map. “We’re happy that the Supreme Court will now have a chance to rule that Democrats – or any political party – will not have a constitutional right to win elections.”